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A guide to the liver

Article date: 10 July 2014

The liver has an array of more than 500 chemical functions that it carries out for the body, most notably ensuring it is able to process and absorb food, working in conjunction with the pancreas, gallbladder and intestines to achieve this.

Located to the right of the body in the upper region of the abdomen, above the pancreas and parts of the intestines, the liver is below the heart and the right lung, and is protected by the ribcage. It is separated from the heart and lungs by a thin sheet of muscle called the diaphragm.

As well as aiding digestion, the liver also produces proteins that help with a range of functions, and detoxifies chemicals and metabolises drugs. Although there are liver dialysis methods that can help in the short term, the organ is necessary for survival.

Keeping it healthy is essential to helping many systems of the body functioning properly, with maintaining a healthy weight, eating well and exercising regularly, while also minimising drug and alcohol intake, all playing a part in keeping the liver operating effectively.

The anatomy of the liver

Red-brown in colour and about five times the size of your fist, the liver is a very complex organ, weighs around three pounds (1.5 kg) and feels rubbery to the touch.

Roughly triangular and comprising two lobes, or halves, the right of which is bigger than the left, it is the largest internal organ and gland in humans. The functional units of the liver are lobules, each consisting of millions of hepatic cells.

Found in all vertebrates, it is divided into a series of independently functioning segments in humans that work alongside a variety of systems and organs throughout the body.

Veins and arteries

Blood flows into the liver through the hepatic artery and the portal vein. The former carries oxygen-rich blood from the heart and the latter transports blood from the gastrointestinal tract, which contains absorbed food material and nutrients.

After it has been treated by the liver, blood flows away from the organ through three hepatic veins that feed a single vein known as the inferior vena cava, which goes to the heart.

Bile duct

The liver rids itself of bile via the common bile duct, a thin tube around the diameter of a drinking straw that is situated at the bottom of the liver and connects it with the intestine.

Bile is produced by the liver and is mixed with food in the gut by the gall bladder, which hangs off the bile duct, storing and squeezing out bile when food and drink is consumed.

How does the liver work?

Operating as the body's chemical laboratory, the primary function of the liver is to filter blood that comes from the digestive tract before it is pumped around the rest of the body by the heart. The liver is also responsible for turning ammonia into urea, which is excreted from the body in urine.

In addition to its functions regarding the processing and absorption of food, the liver also produces a series of proteins that carry out various tasks, including helping blood to clot.

The liver also detoxifies chemicals and metabolises drugs, removing toxins from the body, breaking down proteins and fats, and produces and releases bile to aid digestion.

Bile is a greenish-yellow liquid that helps fat digestion and absorption. It is an alkaline digestive juice that is stored in the gallbladder until needed and is transferred to the duodenum.

In addition to assisting with processing fat from foods, the liver also helps with the use of carbohydrates, which are broken down by the body in glucose that is stored in the liver as glycogen and used as fuel for cells.

As well as glycogen, which is transformed into glucose when the body needs energy, the liver stores an array of other substances, including vitamin A, vitamin K, vitamin B12, vitamin D, copper and iron.

The body needs some cholesterol to function and this is produced by the liver, while the organ also helps to break down old or damaged blood cells.

During the first trimester, the liver is responsible for the majority of red blood cell production, passing over the bulk of the task to bone marrow during gestation.

Hormones that aid growth in children and regulate the production of platelets by bone marrow are also created by the liver, while the organ functions as part of the immune system by processing antigens sent to it.

By carrying out drug metabolism, the liver breaks down medication, modifying toxic substances and ensuring that active ingredients are absorbed into the body to start working.

These are just some of the many functions carried out by the liver, which is also an expandable organ and can act as a blood store should the body require it.

How you can look after your liver

There are more than 100 types of liver disease that affect its healthy functioning, so taking action to ensure it is working at the optimum level is important.

At least two million people in the UK are thought to suffer from liver disease, which can disrupt any number of the 500 plus functions the organ carries out or even cause it to completely fail.

Long-term damage to the liver can lead to permanent scarring of the organ, which is known as cirrhosis and impairs function.

The best way of keeping the liver healthy and preventing damage from being caused to it is by adopting healthy lifestyle factors such as keeping active, eating well, controlling weight, and limiting alcohol and drug intake.

Cirrhosis also has a strong link to the most common form of liver cancer, hepatocellular carcinoma, symptoms of which are often not identified until the disease is at an advanced stage and can include tiredness, rapid weight loss, jaundice and nausea. Rates of liver cancer have risen sharply in the UK during the past few decades, largely as a result of higher levels of obesity and alcohol misuse.

Hepatitis is inflammation of the liver and can be caused by either viral infection by hepatitis A, B or C or by behaviours such as excessive drinking or drug taking, exposure to harmful substances, obesity or allergic reactions.

Non-alcoholic fatty liver disease is caused by a build-up of fat within the organ's cells and is often linked to being overweight or obese.

Gallstones can become trapped in the bile duct and lead to damage to the liver by preventing bile from draining from the organ.

Hemochromatosis is an inherited disorder that leads to a slow build-up of iron within the body that is often deposited around the liver, leading to a range of health problems.

The liver can also be affected or damaged by rarer conditions such as primary binary cirrhosis, which is caused by the immune system attacking bile ducts, or by liver failure by infection.

Treatment for conditions affecting the liver may include transplant and some can prove fatal if they go untreated or are too far advanced when a diagnosis is made.

Protecting the liver by having a healthy and active lifestyle is the best way to guard against liver disease and the risk of developing problems with the organ can be reduced by eating healthily, taking regular exercise, cutting down the threat of infection by hepatitis A, B or C and avoiding excessive drinking or cutting out alcohol completely.

Tests are available to check for liver damage, such as an ultrasound, biopsy or CT scan and indicate whether or not it is functioning healthily. Once the problem has been identified, treatment can begin to reverse or mitigate damage.